Metallic photoresist patterning and defect improvement

ABSTRACT

A multilayer structure for lithography patterning is provided. The multilayer structure includes a substrate, a bottom anti-reflective coating (BARC) layer over the substrate, and a photoresist layer over the BARC layer. The BARC layer includes a polymer and a hydrolysis promoting agent. The photoresist layer includes an organometallic dimer obtained by partial hydrolysis of a precursor organometallic compound comprising hydrolysable ligands.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of U.S. Provisional PatentApplication No. 63/116,636, filed Nov. 20, 2020, which is incorporatedby reference herein in its entirety.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are fabricated bysequentially depositing dielectric layers, conductive layers, andsemiconductor layers over a semiconductor substrate, and patterning thevarious material layers using photolithography. In a photolithographyprocess, a photoresist is deposited over a substrate and is exposed to aradiation such as extreme ultraviolet (EUV) ray. The radiation exposurecauses a chemical reaction in the exposed areas of the photoresist andcreates a latent image corresponding to the mask pattern in thephotoresist. The photoresist is next developed in a developer to removeeither the exposed portions of the photoresist for a positivephotoresist or the unexposed portions of the photoresist for a negativephotoresist. The patterned photoresist is then used as an etch mask insubsequent etching processes in forming integrated circuits (ICs).Advancement in lithography is generally desirable to meet the demand ofthe continued semiconductor miniaturization.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flow chart of a method for fabricating a semiconductorstructure, in accordance with some embodiments.

FIGS. 2A-2H are cross-sectional views of a semiconductor structurefabricated using the method of FIG. 1, in accordance with someembodiments.

FIG. 3 illustrates a first exemplary composition of a middle materiallayer in a patterning stack, in accordance with some embodiments.

FIG. 4 illustrates a second exemplary composition of a middle materiallayer in a patterning stack, in accordance with some embodiments.

FIG. 5 illustrates hydrolysis and condensation of an organotin dimerinduced by a hydrolysis promoting agent in the first exemplarycomposition of the middle material layer of FIG. 3.

FIG. 6 illustrates hydrolysis and condensation of an organotin dimerinduced by a hydrolysis promoting agent in the second exemplarycomposition of the middle material layer of FIG. 4.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. System may be otherwise oriented (rotated 90 degrees or atother orientations) and the spatially relative descriptors used hereinmay likewise be interpreted accordingly.

When describing the compounds, compositions, methods and processes ofthe present disclosure, the following terms have the following meanings,unless otherwise indicated.

As described herein, the compounds disclosed herein may optionally besubstituted with one or more substituents, such as illustrated generallybelow, or as exemplified by particular classes, subclasses, and speciesof the present disclosure. It will be appreciated that the phrase“optionally substituted” is used interchangeably with the phrase“substituted or unsubstituted”. In general, the term “substituted”whether proceeded by the term “optionally” or not, refers to thereplacement of one or more hydrogen radicals in a given structure withthe radical of a specified substituent. Unless otherwise indicated, anoptionally substituted group may have a substituent at eachsubstitutable position of the group. When more than one position in agiven structure can be substituted with more than one substituentselected from a specified group, the substituent may be either the sameor different at each position.

“Alkyl” refers to a straight or branched hydrocarbon chain groupconsisting solely of carbon and hydrogen atoms, containing nounsaturation, having from one to twelve carbon atoms (C₁-C₁₂ alkyl), oneto eight carbon atoms (C₁-C₈ alkyl) or one to six carbon atoms (C₁-C₆alkyl), and which is attached to the rest of the molecule by a singlebond, e.g., methyl, ethyl, n-propyl, 1-methylethyl (iso-propyl),n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl), 3-methylhexyl,2-methylhexyl, and the like. Unless stated otherwise specifically in thespecification, alkyl groups are optionally substituted.

“Alkylene” or “alkylene chain” refers to a straight or branched divalenthydrocarbon chain linking the rest of the molecule to a radical group,consisting solely of carbon and hydrogen, containing no unsaturation,and having from one to twelve carbon atoms, e.g., methylene, ethylene,propylene, n-butylene, ethenylene, propenylene, n-butenylene,propynylene, n-butynylene, and the like. The alkylene chain is attachedto the rest of the molecule through a single bond and to the radicalgroup through a single bond. The points of attachment of the alkylenechain to the rest of the molecule and to the radical group can bethrough one carbon or any two carbons within the chain. Unless statedotherwise specifically in the specification, alkylene is optionallysubstituted.

“Alkenylene” or “alkenylene chain” refers to a straight or brancheddivalent hydrocarbon chain linking the rest of the molecule to a radicalgroup, consisting solely of carbon and hydrogen, containing at least onecarbon-carbon double bond and having from two to twelve carbon atoms,e.g., ethenylene, propenylene, n-butenylene, and the like. Thealkenylene chain is attached to the rest of the molecule through asingle bond and to the radical group through a double bond or a singlebond. The points of attachment of the alkenylene chain to the rest ofthe molecule and to the radical group can be through one carbon or anytwo carbons within the chain. Unless stated otherwise specifically inthe specification, alkenylene is optionally substituted.

“Alkynylene” or “alkynylene chain” refers to a straight or brancheddivalent hydrocarbon chain linking the rest of the molecule to a radicalgroup, consisting solely of carbon and hydrogen, containing at least onecarbon-carbon triple bond and having from two to twelve carbon atoms,e.g., ethenylene, propenylene, n-butenylene, and the like. Thealkynylene chain is attached to the rest of the molecule through asingle bond and to the radical group through a double bond or a singlebond. The points of attachment of the alkynylene chain to the rest ofthe molecule and to the radical group can be through one carbon or anytwo carbons within the chain. Unless stated otherwise specifically inthe specification, alkynylene is optionally substituted.

“Alkoxy” refers to a group of the formula —OR_(a) where R_(a) is analkyl group as defined above containing one to twelve carbon atoms.Unless stated otherwise specifically in the specification, an alkoxygroup is optionally substituted.

“Cycloalkyl” refers to a stable non-aromatic monocyclic or polycycliccarbocyclic ring, which may include fused or bridged ring systems,having from three to fifteen carbon atoms, preferably having from threeto ten carbon atoms, and which is saturated or unsaturated and attachedto the rest of the molecule by a single bond. Monocyclic cyclocalkylsinclude, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptly, and cyclooctyl. Polycyclic cycloalkyls include, forexample, adamantyl, norbornyl, decalinyl,7,7-dimethyl-bicyclo-[2.2.1]heptanyl, and the like. Unless statedotherwise specifically in the specification, a cycloalkyl group isoptionally substituted.

“Aryl” refers to a ring system comprising at least one carbocyclicaromatic ring. In some embodiments, an aryl comprises from 6 to 18carbon atoms. The aryl ring may be a monocyclic, bicyclic, tricyclic ortetracyclic ring system, which may include fused or bridged ringsystems. Aryls include, but are not limited to, aryls derived fromaceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene,benzene, chrysene, fluoranthene, fluorene, as-indacene, s-indacene,indane, indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene,and triphenylene. Unless stated otherwise specifically in thespecification, an aryl group is optionally substituted.

“Heteroaryl” refers to a 5- to 14-membered ring system comprising one tothirteen carbon atoms, one to six heteroatoms selected from the groupconsisting of nitrogen, oxygen and sulfur, and at least one aromaticring. For purposes of certain embodiments of this disclosure, theheteroaryl radical may be a monocyclic, bicyclic, tricyclic ortetracyclic ring system, which may include fused or bridged ringsystems; and the nitrogen, carbon or sulfur atoms in the heteroarylradical may be optionally oxidized; the nitrogen atom may be optionallyquaternized. Examples include, but are not limited to, azepinyl,acridinyl, benzimidazolyl, benzthiazolyl, benzindolyl, benzodioxolyl,benzofuranyl, benzooxazolyl, benzothiazolyl, benzothiadiazolyl,benzo[b][1,4]dioxepinyl, 1,4-benzodioxanyl, benzonaphthofuranyl,benzoxazolyl, benzodioxolyl, benzodioxinyl, benzopyranyl,benzopyranonyl, benzofuranyl, benzofuranonyl, benzothienyl(benzothiophenyl), benzotriazolyl, benzo[4,6]imidazo[1,2-a]pyridinyl,benzoxazolinonyl, benzimidazolthionyl, carbazolyl, cinnolinyl,dibenzofuranyl, dibenzothiophenyl, furanyl, furanonyl, isothiazolyl,imidazolyl, indazolyl, indolyl, indazolyl, isoindolyl, indolinyl,isoindolinyl, isoquinolyl, indolizinyl, isoxazolyl, naphthyridinyl,oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl, 1-oxidopyridinyl,1-oxidopyrimidinyl, 1-oxidopyrazinyl, 1-oxidopyridazinyl,1-phenyl-1H-pyrrolyl, phenazinyl, phenothiazinyl, phenoxazinyl,phthalazinyl, pteridinyl, pteridinonyl, purinyl, pyrrolyl, pyrazolyl,pyridinyl, pyridinonyl, pyrazinyl, pyrimidinyl, pryrimidinonyl,pyridazinyl, pyrrolyl, pyrido[2,3-d]pyrimidinonyl, quinazolinyl,quinazolinonyl, quinoxalinyl, quinoxalinonyl, quinolinyl, isoquinolinyl,tetrahydroquinolinyl, thiazolyl, thiadiazolyl,thieno[3,2-d]pyrimidin-4-onyl, thieno[2,3-d]pyrimidin-4-onyl, triazolyl,tetrazolyl, triazinyl, and thiophenyl (i.e., thienyl). Unless statedotherwise specifically in the specification, a heteroaryl group isoptionally substituted.

The term “substituted” used herein means any of the above groups (e.g.,alkyl, alkylene, alkenylene, alkynylene, heteroalkylene,heteroalkenylene, heteroalkynylene, alkoxy, alkylether,alkoxyalkylether, heteroalkyl, heteroalkoxy, phosphoalkyl,phosphoalkylether, thiophosphoalkyl, thiophosphoalkylether, carbocyclic,cycloalkyl, aryl, heterocyclic and/or heteroaryl) wherein at least onehydrogen atom (e.g., 1, 2, 3 or all hydrogen atoms) is replaced by abond to a non-hydrogen atoms such as, but not limited to: a halogen atomsuch as F, Cl, Br, and I; an oxygen atom in groups such as hydroxylgroups, alkoxy groups, and ester groups; a sulfur atom in groups such asthiol groups, thioalkyl groups, sulfone groups, sulfonyl groups, andsulfoxide groups; a nitrogen atom in groups such as amines, amides,alkylamines, dialkylamines, arylamines, alkylarylamines, diarylamines,N-oxides, imides, and enamines; a silicon atom in groups such astrialkylsilyl groups, dialkylarylsilyl groups, alkyldiarylsilyl groups,and triarylsilyl groups; and other heteroatoms in various other groups.“Substituted” also means any of the above groups in which one or morehydrogen atoms are replaced by a higher-order bond (e.g., a double- ortriple-bond) to a heteroatom such as oxygen in oxo, carbonyl, carboxyl,and ester groups; and nitrogen in groups such as imines, oximes,hydrazones, and nitriles. For example, “substituted” includes any of theabove groups in which one or more hydrogen atoms are replaced with—NR_(g)R_(h), —NR_(g)C(═O)R_(h), —NR_(g)C(═O)NR_(g)R_(h),—NR_(g)C(═O)OR_(h), —NR_(g)SO₂R_(h), —OC(═O)NR_(g)R_(h), —OR_(g),—SR_(g), —SOR_(g), —SO₂R_(g), —OSO₂R_(g), —SO₂OR_(g), ═NSO₂R_(g), and—SO₂NR_(g)R_(h). “Substituted” also means any of the above groups inwhich one or more hydrogen atoms are replaced with —C(═O)R_(g),—C(═O)OR_(g), —C(═O)NR_(g)R_(h), —CH₂SO₂R_(g), and —CH₂SO₂NR_(g)R_(h).In the foregoing, R_(g) and R_(h) are the same or different andindependently hydrogen, alkyl, alkoxy, alkylamino, thioalkyl, aryl,aralkyl, cycloalkyl, cycloalkylalkyl, haloalkyl, heterocyclyl,N-heterocyclyl, heterocyclylalkyl, heteroaryl, N-heteroaryl and/orheteroarylalkyl. “Substituted” further means any of the above groups inwhich one or more hydrogen atoms are replaced by a bond to an amino,cyano, hydroxyl, imino, nitro, oxo, thioxo, halo, alkyl, alkoxy,alkylamino, thioalkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl,haloalkyl, heterocyclyl, N-heterocyclyl, heterocyclylalkyl, heteroaryl,N-heteroaryl and/or heteroarylalkyl group. In addition, each of theforegoing substituents may also be optionally substituted with one ormore of the above substituents.

To continue to reduce device sizes produced from lithography,photolithographic systems have been developed to use extreme ultraviolet(EUV) light which has very short wavelengths (13.5 nm or shorter)thatcan allow very small image formation. However, conventional systems andmethods of performing EUV lithography may have shortcomings. Forexample, conventional photoresist materials are typically organicmaterials. These organic photoresist materials normally have low photonabsorption in the EUV range, which makes achieving high resolution withEUV light difficult. Organometallic oxide hydroxide clusters have beenshown to be useful as suitable EUV photoresist materials for achievingfine patterning. The high EUV absorption cross section and smallbuilding block size of the organometallic oxide hydroxide clusters allowhigh sensitivity and resolution as well as low line-edge roughness.

However, a variety of issues may occur especially at the interface oforganometallic oxide hydroxide clusters and an underlying layer, e.g., abottom anti-reflective coating (BARC) layer. For example, organometallicoxide hydroxide clusters are obtained by hydrolysis of precursororganometallic compounds containing hydrolysable ligands using water inthe ambient atmosphere followed by condensation of hydrolyzedorganometallic compounds. Oftentimes, water in the ambient atmospheredoes not result in the complete hydrolysis of the precursororganometallic compounds at the interface. The partially hydrolyzedorganometallic compounds may couple the organometallic oxide hydroxideclusters to the underlying BARC layer, thereby forming aggregates of theorganometallic oxide hydroxide clusters. It has been observed thatdeposition of organometallic photoresists onto highly polar surfaces,for example surfaces rich in —OH, can lead to formation of aggregates oforganometallic oxide hydroxide clusters. Such aggregates can causehigher levels of scum/broken defects.

Compositions and methods to facilitate complete hydrolysis oforganometallic photoresist precursor compounds are provided. Inembodiments of the present application, a hydrolysis promoting agent isintroduced into a BARC layer underlying the photoresist layer. Thehydrolysis promoting agent can either absorb water from ambientatmosphere or react with an acid or base in the BARC layer to producewater, thereby promoting conversion of partially hydrolyzedorganometallic compound to organometallic oxide hydroxide clusters,which avoid scum formation. This can, in turn, lead to lower defectrates in lithographic patterning and corresponding reductions inintegrated circuit manufacturing costs.

FIG. 1 is a flowchart of a method 100 of forming a semiconductor device,in accordance with some embodiments of the present disclosure. FIGS.2A-2E are cross-sectional views of a semiconductor device 200 fabricatedaccording to one or more steps of the method 100. It is understood thatadditional steps can be provided before, during, and after the method100, and some of the steps described below can be replaced oreliminated, for additional embodiments of the method. It is furtherunderstood that additional features can be added in the semiconductordevice 200, and some of the features described below can be replaced oreliminated, for additional embodiments of the semiconductor device 200.

The semiconductor device 200 may be an intermediate device fabricatedduring processing of an integrated circuit, or portion thereof, that maycomprise static random access memory (SRAM) and/or other logic circuits,passive components such as resistors, capacitors, and inductors, andactive components such as P-channel field effect transistors (PFET),N-channel FET (NFET), metal-oxide semiconductor field effect transistors(MOSFET), complementary metal-oxide semiconductor (CMOS) transistors,bipolar transistors, high voltage transistors, high frequencytransistors, other memory cells, and combinations thereof. Thesemiconductor device 200 includes a plurality of semiconductor devices(e.g., transistors), which may be interconnected.

Referring to FIGS. 1 and 2A, the method 100 include an operation 102, inwhich a bottom material layer 210 is deposited over a substrate 202, inaccordance with some embodiments. FIG. 2A is a cross-sectional view of asemiconductor device 200 after depositing the bottom material layer 210over the substrate 202. The bottom material layer 210 may be a firstlayer of a trilayer patterning stack.

In some embodiments, the substrate 202 is a bulk semiconductor substrateincluding one or more semiconductor materials. In some embodiments, thesubstrate 202 includes silicon, silicon germanium, carbon doped silicon(Si:C), silicon germanium carbide, or other suitable semiconductormaterials. In some embodiments, the substrate 202 is composed entirelyof silicon.

In some embodiments, the substrate 202 includes one or more epitaxiallayers formed on a top surface of a bulk semiconductor substrate. Insome embodiments, the one or more epitaxial layers introduce strains inthe substrate 202 for performance enhancement. For example, theepitaxial layer includes a semiconductor material different from that ofthe bulk semiconductor substrate, such as a layer of silicon germaniumoverlying bulk silicon or a layer of silicon overlying bulk silicongeranium. In some embodiments, the epitaxial layer(s) incorporated inthe substrate 202 are formed by selective epitaxial growth, such as, forexample, metalorganic vapor phase epitaxy (MOVPE), molecular beamepitaxy (MBE), hydride vapor phase epitaxy (HVPE), liquid phase epitaxy(LPE), metal-organic molecular beam epitaxy (MOMBE), or combinationsthereof.

In some embodiments, the substrate 202 is an active layer of asemiconductor-on-insulator (SOI) substrate. In some embodiments, the SOIsubstrate includes a semiconductor layer, such as a silicon layer formedon an insulator layer. In some embodiments, the insulator layer is aburied oxide (BOX) layer including silicon oxide or silicon germaniumoxide. The insulator layer is provided on a handle substrate such as,for example, a silicon substrate. In some embodiments, the SOI substrateis formed using separation by implanted oxygen (SIMOX) or wafer bonding.

The substrate 202 may also include other material layers and othercircuit patterns. In some embodiments, the substrate 202 includesvarious doped regions formed by a process such as ion implantationand/or diffusion. The doped regions are doped with p-type and/or n-typedopants. The term “p-type” refers to the addition of impurities to anintrinsic semiconductor that creates deficiencies of valence electrons.Examples of p-type dopants, i.e., impurities, include, but are notlimited to, boron, boron difluoride, gallium, and indium. The term“n-type” refers to the addition of impurities that contributes freeelectrons to an intrinsic semiconductor. Examples of n-type dopants,i.e., impurities, include, but are not limited to, antimony, arsenic,and phosphorous. In other embodiments, the substrate 202 may furtherinclude one or more material layers to be patterned (by etching toremove or ion implantation to introduce dopants), such as a dielectriclayer to be patterned to form trenches for conductive lines or holes forcontacts or vias; a gate material stack to be patterned to form gates;or a semiconductor material to be patterned to form isolation trenches.For example, a material layer to be patterned is a semiconductor layeras a part of the substrate 202. In other embodiments, multiplesemiconductor material layers, such as gallium arsenic (GaAs) andaluminum gallium arsenic (AlGaAs), are epitaxially grown on thesubstrate 202 and are patterned to form various devices, such aslight-emitting diodes (LEDs). In some other embodiments, the substrate202 includes fin active regions and three dimensional fin field-effecttransistors (FinFETs) formed or to be formed thereon.

The bottom material layer 210 is deposited on the substrate 202. Thebottom material layer 210 functions as a mask to protect the substrate202 from etching or ion implantation. In some embodiments, the bottommaterial layer 210 also functions as a planarization layer to provide aplanar surface upon which a middle material layer 220 (FIG. 2B) isformed. In some embodiments, the bottom material layer 210 includes anorganic polymer free of silicon. For example, the bottom material layer210 may include spin-on carbon, diamond-like carbon, polyarylene ether,or polyimide. In some embodiments, the bottom material layer 210 isformed by spin coating, spry coating, dip coating, or other suitabledeposition processes. The bottom material layer 210 is formed to have athickness sufficient to provide a planar surface and etching resistance.In some embodiments, the bottom material layer 210 may have a thicknessranging from about 50 nm to about 300 nm. If the thickness of the bottommaterial layer 210 is too small, the bottom material layer 210 is notable to provide a planar surface and sufficient etching resistance, insome instances. On the other hand, if the thickness of the bottommaterial layer 210 is too great, production costs are increased as aresult of unnecessary consumption of material and increased processingtime to pattern the bottom material layer 210, in some instances.

Referring to FIGS. 1 and 2B, the method 100 proceeds to operation 104,in which a middle material layer 220 is deposited over the bottommaterial layer 210, in accordance with some embodiments. FIG. 2B is across-sectional view of the semiconductor device 200 of FIG. 2A afterdepositing the middle material layer 220 over the bottom material layer210. The middle material layer 220 may be a second layer of the trilayerpatterning stack.

The middle material layer 220 includes a material that provides etchingselectivity from the bottom material layer 210. The middle materiallayer 220 thus functions as an etch mask to transfer a pattern to thebottom material layer 210. In some embodiments, the middle materiallayer 220 also functions as a bottom anti-reflective coating (BARC)layer that reduces reflection during a lithography exposure processsubsequently performed, thereby increasing the imaging contrast andenhancing the imaging resolution. In embodiments of the presentdisclosure, the middle material layer 220 includes a hydrolysispromoting agent 320 to facilitate the complete hydrolysis andcondensation of pre-hydrolyzed organometallic photoresist materialssubsequently formed thereon.

FIG. 3 illustrates a first exemplary composition 300 of the middlematerial layer 220, in accordance with some embodiments. As shown inFIG. 3, the middle material layer 220 may include a polymer 310, ahydrolysis promoting agent 320, and one or more additives 330.

The polymer 310 may be an organic polymer or inorganic polymer. In someembodiments, the polymer 310 has a molecular weight from about 1,000 toabout 20,000. In some embodiments, the polymer 310 is a copolymerconsisting of two or more different monomers. Each monomer introduces ortunes a specific property of the polymer 310. In some embodiments, thepolymer 310 is polystyrene (PS), poly(hydroxystyrene) (PHS), poly(methylmethacrylate) (PMMA), a polyether, a polyimide, a polyurethane, asiloxane polymer, or a copolymer thereof, each of which can includedifferent pedant groups attached to the polymer backbone 312. In someembodiments, the pedant groups include first pedant groups 314 (labeledas “A”) that provide crosslinking sites, second pedant groups 316(labeled as “B”) containing chromophores that modify the characteristics(such as refractive index n, extinction coefficient κ, and/or etchresistance) of the middle material layer 220, and third pedant groups318 (labeled as “C”) that enhance the adhesion of a photoresist layersubsequently formed and tune other effects, such as etching performanceand wet strippability.

In some embodiments, the first pedant group (A) 314 is a cross-linkerwhich functions to cross-link various components in the middle materiallayer 220 into a polymer network. In some embodiments, the cross-linkeris an alkyl group having 2-20 carbons (C2-C20) with at least onecrosslinkable functional group, such as —I, —Br, —Cl, —NH₂, —COOH, —OH,—SH, —N₃, epoxy, alkyne, alkene, ketone, aldehyde, ester, acyl halide,NHS ester, imidoester, pentafluorophenyl ester, hydroxymethyl phosphine,carbodiimide, maleimide, haloacetyl, pyridyldisulfide, thiosulfonate,vinylsulfone, hydrazide, alkoxyamine, diazirine, aryl azide, isocyanate,phosphine, amide, ether, or a combination thereof.

In some embodiments, the second pendant group (B) 316 includes an alkylgroup having 3-20 carbons (C3-C20) with at least one light-sensitivefunctional group, such as aromatic groups or heteroaryl groups, capableof absorbing the impinging light and preventing the light from beingreflected. Exemplary aromatic groups include, but are not limited to,phenyl, napthlenyl, phenanthrenyl, anthracenyl, phenalenyl, pyrene,perylene, and other aromatic derivatives containing three or more rings.Exemplary heteroaryl groups include, but are not limited to, acridine,pyrrolidinyl, pyranyl, piperidinyl, and quinolinyl.

In some embodiments, the third pendant group (C) 318 includes an alkylgroup having 1-20 carbons (C1-C20) with a non-cyclic structure or acyclic structure. For example, the cyclic structure is an aromatic ring.The third pendant group 318 is adapted to enhance photoresist adhesion,etching resistance, and wet strippability. In other examples, the alkylgroup further includes a functionalized group, such as —I, —Br, —Cl,—NH₂, —COOH, —OH, —SH, —N₃, —S(═O)—, alkene, alkyne, imine, ether,ester, aldehyde, ketone, amide, sulfone, acetic acid, cyanide, or acombination thereof.

In some embodiments, the middle material layer 220 includes a hydrolysispromoting agent (S) 320 for facilitating complete hydrolysis andcondensation of an organometallic photoresist subsequently formedthereon during the organometallic photoresist soft baking process. Insome embodiments, the hydrolysis promoting agent (S) 320 is adapted toabsorb water from the ambient environment to facilitate completehydrolysis and condensation of the organometallic photoresist. In someembodiments, the hydrolysis promoting agent (S) 320 can be a highboiling point solvent or a diffusible molecule containing one or morepolar functional groups. In some embodiments, the high boiling pointsolvent includes dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC),dimethyl formamide (DMF), ortho, meta or para-toluidine, p-toluenesulfonic acid, pyridine, chlorobenzene, tetrachloroethane, cumene,propionic acid, 1-hexanol, m-butanol, or acetic acid. In someembodiments, the diffusible molecule has the formula (I):

R₁—X  (I)

In the formula (I), R₁ is an alkyl, cycloalkyl or aryl group and X is apolar functional group. Exemplary groups for R₁ include methyl, ethyl,propyl, butyl, pentyl, hexyl, benzyl, phenethyl, naphthyl; phenoxy,methylphenoxy, dimethylphenoxy, ethylphenoxy, and phenyloxy-methyl.Exemplary groups for X include —I, —Br, —Cl, —NH₂, —COOH, —OH, —SH, —N₃,—S(═O)—, imine, ether, ester, aldehyde, ketone, amide, sulfone, aceticacid, cyanide, phosphine, phosphite, aniline, pyridine, and pyrrole.

In some embodiments, the high boiling point solvent or the diffusiblemolecule has a boiling point greater than 180° C. such that after bakingof the middle material layer 220, the polar solvent or diffusiblemolecule can remain in the middle material layer 220 to assist thehydrolysis of organometallic photoresist materials during theorganometallic photoresist soft-baking process.

In some embodiments, the middle material layer 220 may further includeone or more additives 330 adapted to modify the characteristics andenhance the performance (such as wettability and accordingly enhancingthe cleaning mechanism during the cleaning process) of the middlematerial layer 220. For example, in some embodiments, the middlematerial layer 220 may include a surfactant for improving the ability ofthe middle material layer 220 to coat the surface on which it is applied(e.g., the top surface of the bottom material layer 210). In someembodiments, the surfactant may include nonionic surfactants, polymershaving fluorinated aliphatic groups, surfactants that contain at leastone fluorine atom and/or at least one silicon atom, polyoxyethylenealkyl ethers, polyoxyethylene alkyl aryl ethers,polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acidesters, polyoxyethylene sorbitan fatty acid esters.

Specific examples of materials that may be used as surfactants include,but are not limited to, polyoxyethylene lauryl ether, polyoxyethylenestearyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether,polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether,sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,sorbitan monooleate, sorbitan trioleate, sorbitan tristearate,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate, polyethyleneglycol distearate, polyethylene glycol dilaurate, polyethylene glycol,polypropylene glycol, polyoxyethylenestearyl ether and polyoxyethylenecetyl ether; fluorine containing cationic surfactants, fluorinecontaining nonionic surfactants, fluorine containing anionicsurfactants, cationic surfactants and anionic surfactants, combinationsof these, and the like.

Another additive that may be added to the middle material layer 220 is aquencher, which may be utilized to inhibit diffusion of the generatedacids/bases/free radicals within the middle material layer 220, andthereby helps to improve the stability of the middle material layer 220over time. In some embodiments, the quencher is an amine such as asecond lower aliphatic amine, a tertiary lower aliphatic amine, or thelike. Specific examples of amines that may be used include, but are notlimited to, trimethylamine, diethylamine, triethylamine,di-n-propylamine, tri-n-propylamine, tripentylamine, diethanolamine,triethanolamine, alkanolamine, combinations of these, and the like.

Alternatively, an organic acid may be utilized as the quencher. Specificexamples of organic acids that may be utilized include, but are notlimited to, malonic acid, citric acid, malic acid, succinic acid,benzoic acid, salicylic acid, phosphorous oxo acid and its derivativessuch as phosphoric acid and derivatives thereof such as its esters, suchas phosphoric acid, phosphoric acid di-n-butyl ester and phosphoric aciddiphenyl ester; phosphonic acid and derivatives thereof such as itsester, such as phosphonic acid, phosphonic acid dimethyl ester,phosphonic acid di-n-butyl ester, phenylphosphonic acid, phosphonic aciddiphenyl ester, and phosphonic acid dibenzyl ester; and phosphinic acidand derivatives thereof such as its esters, including phosphinic acidand phenylphosphinic acid.

FIG. 4 illustrates a second exemplary composition 400 of the middlematerial layer 220, in accordance with some embodiments. As shown inFIG. 4, the middle material layer 220 may include a polymer 310 asdescribed above in FIG. 3, a hydrolysis promoting agent (W) 420, an acidor base generator 422, and one or more additives 330 as described abovein FIG. 3.

Unlike the hydrolysis promoting agent (S) 320 in the first exemplarycomposition 300, which is a high boiling point solvent or a diffusiblemolecule adapted to absorb water from ambient environment, thehydrolysis promoting agent (W) 420 in the second exemplary composition400 is a water releasable compound that can release water in acid orbasic conditions to facilitate the complete hydrolysis and condensationof the organometallic photoresist materials. In some embodiments, thehydrolysis promoting agent (W) 420 is an organic compound containing oneor more OH groups. In some embodiments, the hydrolysis promoting agent(W) 420 includes an alcohol such as ethanol, 1-butanol, 1-propanol,2-propanol, 2-butanol, isobutyl alcohol, 1-pentanol, 2-pentanol, or2-methyl-2-pentanol. In some other embodiments, the hydrolysis promotingagent (W) 420 includes a diol containing an alkyl group of at least twocarbon atoms and two OH groups such as propylene glycol, ethyleneglycol, or 1,3-propanediol. In still some embodiments, the hydrolysispromoting agent (W) 420 includes a polyol containing an alkyl group ofat least two carbon atoms and more than two OH groups such as glycerin,trimethylolpropane, or pentaerythritol. The alcohol, diol or polyol mayfurther include a functional group such as —I, —Br, —Cl, —NH₂, —COOH,—OH, —SH, —N₃, —S(═O)—, imine, ether, ester, aldehyde, ketone, amide,sulfone, acetic acid, cyanide, phosphine, phosphite, aniline, pyridine,or pyrrole.

The acid or base generator 422 functions as a cross-linking accelerator,which promotes the cross-linking reaction and increases the reactionefficiency of the polymer 310. In some embodiments, the acid generatoris a thermal acid generator (TAG) capable of releasing an acid uponthermal treatment. Exemplary thermal acid generators that are suitablyemployed include, but are not limited to,2,4,4,6-tetrabromocyclohexadienone, 2-hydroxyhexyl p-toluenesulfonate,2-nitrophenyl tosylate and other alkyl esters of organic sulfonic acids.In some embodiments, the base generator is a thermal base generator(TBG) capable of releasing a base upon thermal treatment. The thermalbase generator may comprise a compound belonging to a group such asamides, sulfonamides, imides, imines, O-acyl oximes, benzoyloxycarbonylderivatives, quarternary ammonium salts, and nifedipines, examples ofwhich may include o-{(β(dimethylamino) ethyl)aminocarbonyl benzoic acid,o-{(γ(dimethylamino)propyl) aminocarbonyl}benzoic acid,2,5-bis{(β-(dimethylamino) ethyl)aminocarbonyl}terephthalic acid,2,5-bis{(γ-(dimethylamino)propyl)aminocarbonyl} terephthalic acid,2,4-bis{(β-(dimethylamino)ethyl)aminocarbonyl}isophthalic acid, and2,4-bis{(γ-(dimethylamino)propyl) aminocarbonyl} isophthalic acid.

To form the middle material layer 220, various components of the middlematerial layer 220 are placed into a solvent in order to aid in themixing and application of the middle material layer 220. In someembodiments, the solvent may be an organic solvent such as ketones,alcohols, polyalcohols, ethers, glycol ethers, cyclic ethers, aromatichydrocarbons, esters, propionates, lactates, lactic esters, alkyleneglycol monoalkyl ethers, alkyl lactates, alkyl alkoxypropionates, cycliclactones, monoketone compounds that contain a ring, alkylene carbonates,alkyl alkoxyacetate, alkyl pyruvates, ethylene glycol alkyl etheracetates, diethylene glycols, propylene glycol alkyl ether acetates,alkylene glycol alkyl ether esters, alkylene glycol monoalkyl esters, orthe like.

Exemplary solvents that can be used for formation of middle materiallayer 220 include, but are not limited to, acetone, methanol, ethanol,toluene, xylene, 4-hydroxy-4-methyl-2-pentatone, tetrahydrofuran, methylethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone,ethylene glycol, ethylene glycol monoacetate, ethylene glycol dimethylether, ethylene glycol methylethyl ether, ethylene glycol monoethylether, methyl cellosolve acetate, ethyl cellosolve acetate, diethyleneglycol, diethylene glycol monoacetate, diethylene glycol monomethylether, diethylene glycol diethyl ether, diethylene glycol dimethylether, diethylene glycol ethylmethyl ether, diethylene glycol monoethylether, diethylene glycol monobutyl ether, ethyl 2-hydroxypropionate,methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate,ethyl ethoxyacetate, ethyl hydroxyacetate, methyl2-hydroxy-2-methylbutanate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, methyl 3-ethoxypropionate, ethyl3-ethoxypropionate, ethyl acetate, butyl acetate, methyl lactate andethyl lactate, propylene glycol, propylene glycol monoacetate, propyleneglycol monoethyl ether acetate, propylene glycol monomethyl etheracetate, propylene glycol monopropyl methyl ether acetate, propyleneglycol monobutyl ether acetate, propylene glycol monobutyl etheracetate, propylene glycol monomethyl ether propionate, propylene glycolmonoethyl ether propionate, propylene glycol methyl ether adcetate,proplylene glycol ethyl ether acetate, ethylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, propylene glycolmonomethyl ether, propylene glycol monoethyl ether, propylene glycolmonopropyl ether, propylene glycol monobutyl ether, ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, propyl lactate, butyllactate, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, methyl3-ethoxypropionate, and ethyl 3-methoxypropionate, β-propiolactone,β-butyrolactone, γ-butyrolactone, α-methyl-γ-butyrolactone,β-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-octanoiclactone, α-hydroxy-γ-butyrolactone, 2-butanone, 3-methylbutanone,pinacolone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone,2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone,3-decanone, 4-decanone, 5-hexene-2-one, 3-pentene-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methylcycloheptanone, 3-methylcycloheptanone, pylene carbonate,vinylene carbonate, ethylene carbonate, butylene carbonate,acetate-2-methoxyethyl, acetate-2-ethoxyethyl,acetate-2-(2-ethoxyethoxyl)ethyl, acetate-3-methoxy-3-methylbutyl,acetate-1-methoxy-2-propyl, dipropylene glycol, monomethylether,monoethylether, monopropylether, monobutylether, monophenylether,dipropylene glycol monoacetate, dioxane, methyl acetate, ethyl acetate,butyl acetate, methyl puruvate, ethyl puruvate, propyl pyruvate, methylmethoxypropionate, ethyl ethoxypropionate, n-methylpyrrolidone (NMP),2-methoxyethyl ether (diglyme), ethylene glycol monom-ethyl ether,propylene glycol monomethyl ether, methyl proponiate, ethyl proponiate,ethyl ethoxy proponiate, methylethyl ketone, cyclohexanone, 2-heptanone,carbon dioxide, cyclopentatone, cyclohexanone, ethyl 3-ethocypropionate,ethyl lactate, propylene glycol methyl ether acetate (PGMEA), methylenecellosolve, butyle acetate, 2-ethoxyethanol, N-methylformamide,N,N-dimethylformamide, N-methylformanilide, N-methylacetamide,N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, benzylethyl ether, dihexyl ether, acetonylacetone, isophorone, caproic acid,caprylic acid, 1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate,ethyl benzoate, diethyl oxalate, diethyl maleate, γ-butyrolactone,ethylene carbonate, propylene carbonate, and phenyl cellosolve acetate.

Once the solution containing various components of the middle materiallayer 220 has been prepared, the solution is applied onto the bottommaterial layer 210, if present, or onto the substrate 202 by, forexample, spin coating.

Subsequently, a pre-baking process is performed to cure and dry themiddle material layer 220 prior to application of a photoresist layer230 (FIG. 2D). The curing/drying of the middle material layer 220removes the solvent from the middle material layer 220 but thehydrolysis promoting agent 320 remains. In some embodiments, thepre-baking process may be performed at a temperature and for a timeperiod suitable to evaporate the solvent but not the hydrolysispromoting agent 320. For example, in some embodiments, the pre-bakingprocess is performed at a temperature between about 40° C. and 180° C.for about 10 seconds to about 5 minutes. Additionally, the pre-bakingprocess will cause the cross-linking of the polymer 310 to provide agood solvent resistance to the middle material layer 220, so as to allowapplication of the photoresist layer 230 without dissolving the middlematerial layer 220.

Referring to FIGS. 1 and 2C, the method 100 proceeds to operation 106,in which a photoresist layer 230 is deposited over the middle materiallayer 220, in accordance with some embodiments. FIG. 2C is across-sectional view of the semiconductor device 200 of FIG. 2B afterdepositing the photoresist layer over the middle material layer. Thephotoresist layer 230 may be a top material layer of the trilayerpatterning stack.

In some embodiments, the photoresist layer 230 is a photosensitive layeroperable to be patterned by an EUV radiation. In some embodiments, thephotoresist layer 230, as deposited, comprises a partially hydrolyzedorganometallic compound obtained from in situ hydrolysis of a precursororganometallic compound having the formula (II):

R_(n)-M-L_(4-n)  (II)

In the formula (II), M is a metal with a high EUV radiation-absorptioncross-section. Exemplary metals having a high EUV radiation-absorptioncross-section include, but are not limited to, tin (Sn), antimony (Sb),and indium (In). R is a cleavable organic ligand that can be cleavedunder the EUV radiation to form metal oxo clusters. In some embodiments,R, at each occurrence, is independently an alkyl group having 1 to 12carbon atoms or an aryl group having 5 to 30 carbon atoms. Exemplarygroups for R include, but are not limited to, methyl, ethyl, propyl,butyl, pentyl, hexyl, benzyl, phenethyl, and naphthyl. L, at eachoccurrence, is independently a hydrolysable ligand that can be replacedwith a hydroxy group through a reaction with water. Exemplaryhydrolysable ligands include, but are not limited to, an alkoxy group,an aryloxy group, a halogen atom, an acetoxy group, an acyloxy group, anisocyanate group, and the like. In some embodiments, the hydrolyzablegroup is an alkoxy group such as a methoxy group, an ethoxy group, apropoxt group, or a butoxy group. n is an integer of 1 or 2.

In some embodiments, the in situ hydrolysis of the precursororganometallic compound of formula (II) forms an organometallic dimer M2having the structure of (R_(n)M)₂(OH)₂L_(4-n)(H₂O)₂. In someembodiments, where M is tin, such precursor organometallic compoundincludes t-butyl tris(dimethylamino) tin, i-butyl tris(dimethylamino)tin, n-butyl tris(dimethylamino) tin, sec-butyl tris(dimethylamino) tin,ipropyl(tris)dimethylamino tin, n-propyl tris(diethylamino) tin, andanalogous alkyl(tris)(t-butoxy) tin compounds such as t-butyltris(t-butoxy) tin, i-butyl tris(tbutoxy) tin, n-butyl tris(t-butoxy)tin, sec-butyl tris(t-butoxy) tin, i-propyl(tris) butoxy tin, n-propyltris(t-butoxy) tin, as well as halogen substituted forms of thesematerials. In some examples, the organometallic compound may includet-butyltrichlorotin, i-butyltrichlorotin, n-butyltrichlorotin,sec-butyltrichlorotin, ipropyltrichlorotin, n-propyltrichlorotin,t-butyltribomotin, i-butyltribomotin, nbutyltribomotin,sec-butyltribomotin, i-propyltribromotin, n-propyltribromotin, etc. Inembodiments, the precursor organometallic compound isn-butyltrichlorotin (C₄H₉SnCl₃), and the resulting organometallic dimeris the organotin dimer Sn2 having the structure of(C₄H₉Sn)₂(OH)₂Cl₄(H₂O)₂.

In some embodiments, the photoresist layer 230 further includes asurfactant, a quencher, or a photoacid generator (PAG) that produces anacid upon radiation. Examples of suitable surfactants and quenches areprovided above with respect to middle material layer 220. PAGs currentlyused in photoresists are ionic PAGs. Ionic PAGs are typically saltscomprising a photoactive cation and an anion. Exemplary PAG anionsinclude antimony fluoride (SbF₆ ⁻), and phosphorus fluoride (PF₆ ⁻⁾.These materials respectively react to form hydrogen hexafluoroantimonate(HSbF₆) and fluorophosphoric acid (HPF₆), respectively, upon UVexposure. Exemplary PAG cations include triarylsulfonium anddiaryliodonium.

In some embodiments, the photoresist layer 230 is formed by firstdissolving the precursor organometallic compound of formula (II) in asuitable organic solvent to provide a precursor solution. Exemplarysolvents that can be used to prepare the precursor solution include, butare not limited to, aromatic compounds (e.g., xylenes, toluene), ethers(anisole, tetrahydrofuran), esters (propylene glycol monomethyl etheracetate, ethyl acetate, ethyl lactate), alcohols (e.g.,4-methyl-2-propanol, 1-butanol, methanol, isopropyl alcohol,1-propanol), ketones (e.g., methyl ethyl ketone), mixtures thereof, andthe like. In the precursor solution, the precursor organometalliccompound R_(n)-M-L_(4-n) undergoes in situ -M-L hydrolysis in thepresence of water to form the partially hydrolyzed organometallic dimerM2. Subsequently, the precursor solution is applied onto the middlematerial layer 220 to produce the photoresist layer 230 comprised of theorganometallic dimer M2.

Referring to FIGS. 1 and 2D, the method 100 proceeds to operation 108,in which a baking process 232 is performed to the semiconductor device200, in accordance with some embodiments. FIG. 2D is a cross-sectionalview of the semiconductor device 200 after performing the baking process232. Since this baking process 232 is performed before exposing thephotoresist layer 230 to an EUV radiation, the baking process 232 isalso referred to as a pre-exposure-baking process. Thepre-exposure-baking process 232 removes the solvent from the photoresistlayer 230. In some embodiments, the pre-exposure-baking process 232 isconducted at a temperature ranging from 50° C. to about 150° C. for aduration from about 30 seconds to about 300 seconds.

During the pre-exposure-baking baking process 232, the organometallicdimer M2 undergoes further hydrolysis in the presence of water. Theresulting M-OH or M-OH₂ ligands after hydrolysis may then react witheach other via subsequent condensation to form an organometallic oxidehydroxide cluster with desired photoresist properties. In someembodiments, the organometallic oxide hydroxide cluster is anorganometallic dodecamer cluster having the structure of[(RM)₁₂O₁₄(OH)₆]L₂. In some embodiments, the organometallic dodecamercluster is an organotin dodecamer cluster (Sn12) having the structure of[(BuSn)₁₂O₁₄(OH)₆]L₂. The organotin dodecamer cluster contains twelve Snatoms with alkyl ligands as well as bridging hydroxo and oxo ligands.The organometallic oxide hydroxide cluster does not contain active andhydrolysable ligands, and thus is more stable than the organometallicdimer.

In the present disclosure, the hydrolysis promoting agent 320 or 420 inthe underlying middle material layer 220 facilitates the completehydrolysis of the organometallic dimer, which leads to high conversionfrom the organometallic dimer M2 to the organometallic oxide hydroxidecluster. In this way, the scum caused by aggregation of organometallicoxide hydroxide clusters in the presence of organometallic dimers thatwould otherwise bridge over proximate resist patterns is prevented. As aresult, the photoresist profile is improved, which in turn helps toincrease the product yields and reduce the manufacturing cost.

FIG. 5 illustrates hydrolysis and condensation of an organotin dimer Sn2induced by the hydrolysis promoting agent 320. As shown in FIG. 5, thehigh boiling point solvent or diffusible compound absorbs water from theambient atmosphere. Water can diffuse into the photoresist layer 230 tohydrolyze the hydrolysable ligands in the organotin dimer Sn2, formingfree hydroxyl groups. The subsequent condensation of the hydroxyl groupsaffords the organotin dodecamer cluster Sn12.

FIG. 6 illustrates hydrolysis and condensation of an organotin dimer Sn2induced by the hydrolysis promoting agent (W) 420. As shown in FIG. 6,the water releasable compound (W) can react with the residue acid orbase generator 422 in the middle material layer 220, and thus releaseswater. The generated water can diffuse into the photoresist layer 230 tohydrolyze the hydrolyzable ligands in the organotin dimer Sn2, formingfree hydroxyl groups. The subsequent condensation of the hydroxyl groupsaffords the organotin dodecamer cluster Sn12.

Referring to FIGS. 1 and 2E, the method 100 proceeds to operation 110,in which the photoresist layer 230 is exposed to a patterning radiation240 to form a pattern in the photoresist layer 230, in accordance withsome embodiments. FIG. 2E is a cross-sectional view of the semiconductordevice 200 after forming the pattern in the photoresist layer 230.

As shown in FIG. 2E, the photoresist layer 230 includes exposed portions230A and unexposed portions 230B. The patterning radiation 240 causescleavage of M-C bonds and crosslinking of the organometallic oxidehydroxide clusters in the exposed portions 230A of the photoresist layer230, and results in a stable metal oxide (MO_(x)) with a high level ofresistance to a developer subsequently used.

The patterning radiation has a wavelength less than 250 nm. In someembodiments, the patterning radiation 240 is a deep ultraviolet (DUV)radiation such as KrF excimer laser (248 nm) or ArF excimer laser (193nm), an EUV radiation (13.5 nm), an e-beam radiation, an x-rayradiation, an ion beam radiation, or other suitable radiations. In someembodiments, the photoresist layer 230 is exposed to an EUV radiationbeam with exposure energy from about 10 mJ/cm² to about 60 mJ/cm². Ifthe exposure energy is too high, the efficiency of patterning does notchange but production cost increases, in some instances. If the exposureenergy is too low, the efficiency of patterning is too low, in someinstances. In some embodiments, operation 110 is performed in a liquid(immersion lithography) or in a vacuum for EUV lithography and e-beamlithography.

Subsequently, the photoresist layer 230 may be subjected to apost-exposure bake process. The post-exposure bake process may beperformed at a temperature from about 50° C. to about 200° C. for aduration from about 60 seconds to about 360 seconds.

Referring to FIGS. 1 and 2F, the method 100 proceeds to operation 112,in which the photoresist layer 230 is developed using a developer toform a patterned photoresist layer 230P, in accordance with someembodiments. FIG. 2F is a cross-sectional view of the semiconductordevice of FIG. 2E after forming the patterned photoresist layer 230P.

During the developing process, the developer is applied to thephotoresist layer 230. The developer may remove the exposed or unexposedportions 230A, 230B depending on the resist type. For example and asshown in FIG. 2F, the photoresist layer 230 comprises a negative-typeresist, so the exposed portions 230A are not dissolved by the developerand remain over the middle material layer 220 after the developingprocess. If the photoresist layer 230 comprises a positive-type resist,the exposed portions 230A would be dissolved by the developer, leavingthe unexposed portions 230B over the middle material layer 220 after thedeveloping process.

The remaining exposed portions 230A (or unexposed portions 230B) definea pattern in the patterned photoresist layer 230P. The pattern containsone or more openings that expose portions of the underlying middlematerial layer 220. Because of the small size of the organometallicoxide hydroxide clusters, the pattern in the patterned photoresist layer230P is able to define features with pitches from about 24 nm to about36 nm.

The developer may include alcohols, aromatic hydrocarbons, and the like.Examples of alcohols include, but are not limited to, methanol, ethanol,1-butanol, and 4-Methyl-2-pentanol. Examples of aromatic hydrocarbonsinclude, but are not limited to, xylene, toluene and benzene. In someembodiments, the developer is selected from at least one of methanol,4-Methyl-2-pentanol and xylene.

The developer may be applied using any suitable methods. In someembodiments, the developer is applied by dipping the structure of FIG.2E into a developer bath. In some embodiments, the developing solutionis sprayed into the photoresist layer 230.

Referring to FIGS. 1 and 2G, the method 100 proceeds to operation 114,in which the middle material layer 220 is etched using the patternedphotoresist layer 230P as an etch mask, in accordance with someembodiments. FIG. 2G is a cross-sectional view of the semiconductordevice 200 of FIG. 2F after etching the middle material layer 220 usingthe patterned photoresist layer 230P as an etch mask.

Referring to FIG. 2G, the middle material layer 220 is etched, using thepatterned photoresist layer 230P as an etch mask, to form a patternedmiddle material layer 220P. The etch can be a dry etch such as RIE or awet etch. Etching of the middle material layer 220 exposes portions ofthe underlying bottom material layer 210. If not completely consumedduring the etching process, after etching the middle material layer 220,the patterned photoresist layer 230P is removed by, for example,stripping or oxygen plasma.

Referring to FIGS. 1 and 2H, the method 100 proceeds to operation 116,in which the bottom material layer 210 is etched using the patternedmiddle material layer 220P as an etch mask, in accordance with someembodiments. FIG. 2H is a cross-sectional view of the semiconductordevice 200 of FIG. 2G after etching the bottom material layer 210 usingthe patterned middle material layer 220P as an etch mask.

Referring to FIG. 2H, the bottom material layer 210 is etched, using thepatterned middle material layer 220P as an etch mask, to form apatterned bottom material layer 210P. Etching of the bottom materiallayer 210 exposes portions of the underlying substrate 202

An etching process may be performed to transfer the pattern in thepatterned middle material layer 220P to the bottom material layer 210.In some embodiments, the etching process is an anisotropic etch such asa dry etch. In some embodiments, the dry etch is a RIE or a plasma etch.

One or more fabrication processes, such as an etching process or animplantation process, may be performed to the substrate 202 using thepatterned middle material layer 220P and the patterned bottom materiallayer 210P as a mask.

One aspect of this description relates to a multilayer structure. Themultilayer structure includes a substrate, a bottom anti-reflectivecoating (BARC) layer over the substrate and including a polymer and ahydrolysis promoting agent, and a photoresist layer over the BARC layer.The photoresist layer includes an organometallic dimer obtained bypartial hydrolysis of a precursor organometallic compound represented bythe formula R_(n)-M-L_(4-n), wherein M is a metal selected from thegroup consisting of tin (Sn), antimony (Sb) and indium (In), R is anorganic ligand with 1 to 30 carbon atoms bound to M with a metal-carbonbond, L is a hydrolysable ligand, and n is an integer of 1 or 2.

Another aspect of this description relates to method of forming asemiconductor device. The method includes forming a bottomanti-reflective coating (BARC) layer over a substrate. The BARC layerincludes a polymer and a hydrolysis promoting agent capable of absorbingwater from ambient atmosphere. Next, a photoresist layer is depositedover the BARC layer. The photoresist layer includes an organometallicdimer obtained by partial hydrolysis of a precursor organometalliccompound represented by the formula R_(n)-M-L_(4-n), wherein M is ametal selected from the group consisting of tin (Sn), antimony (Sb) andindium (In), R is an organic ligand with 1 to 30 carbon atoms bound to Mwith a metal-carbon bond, L is a hydrolysable ligand, and n is aninteger of 1 or 2. Next, the photoresist layer is thermally cured,thereby causing hydrolysis of the organometallic dimer in the presenceof water and subsequent condensation of the hydrolyzed organometallicdimer to form an organometallic oxide hydroxide cluster, wherein thehydrolysis promoting agent absorbs water from ambient atmosphere tocause the complete hydrolysis of organometallic dimer. Next, thephotoresist layer is patterned to form a patterned photoresist layer.Next, the BARC layer is etched using the patterned photoresist layer asan etch mask.

Still another aspect of this description relates to a method of forminga semiconductor device. The method includes forming a first materiallayer over a substrate and then forming a second material layer overfirst material layer. The second material layer includes a polymer, athermal acid generator and a hydrolysis promoting agent capable ofreacting with the thermal acid generator to generate water. Next, aprecursor solution is applied over the second material layer to form aphotoresist layer. The precursor solution includes an organometallicdimer obtained by partial hydrolysis of a precursor organometalliccompound represented by the formula R_(n)-M-L_(4-n), wherein M is ametal selected from the group consisting of tin (Sn), antimony (Sb) andindium (In), R is an organic ligand with 1 to 30 carbon atoms bound to Mwith a metal-carbon bond, L is a hydrolysable ligand, and n is aninteger of 1 or 2. Next, the photoresist layer is baked at an elevatedtemperature. The baking the photoresist layer results in hydrolysis ofthe organometallic dimer in the presence of water and subsequentcondensation of the hydrolyzed organometallic dimer forming anorganometallic oxide hydroxide cluster. The water is generated by thereaction of the hydrolysis promoting agent and the thermal acidgenerator. Next, the photoresist layer is exposed to a patterningradiation to form a patterned photoresist layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A multilayer structure, comprising: a substrate;a bottom anti-reflective coating (BARC) layer over the substrate, theBARC layer comprising a polymer and a hydrolysis promoting agent; and aphotoresist layer over the BARC layer, the photoresist layer comprisingan organometallic dimer obtained by partial hydrolysis of a precursororganometallic compound represented by the following formula:R_(n)-M-L_(4-n), wherein: M is a metal selected from the groupconsisting of tin (Sn), antimony (Sb) and indium (In); R is an organicligand with 1 to 30 carbon atoms bound to M with a metal-carbon bond; Lis a hydrolysable ligand; and n is an integer of 1 or
 2. 2. Themultilayer structure of claim 1, wherein the hydrolysis promoting agentcomprises a high boiling point solvent having a boiling point greaterthan 180° C.
 3. The multilayer structure of claim 2, wherein the highboiling point solvent comprises dimethyl sulfoxide (DMSO),dimethylacetamide (DMAC), dimethyl formamide (DMF), toluidine, p-toluenesulfonic acid, pyridine, chlorobenzene, tetrachloroethane, cumene,propionic acid, 1-hexanol, m-butanol or acetic acid.
 4. The multilayerstructure of claim 1, wherein the hydrolysis promoting agent comprises adiffusible molecule represented by the following formula:R₁—X, wherein: R₁ is an alkyl, cycloalkyl or aryl group; and X is —I,—Br, —Cl, —NH₂, —COOH, —OH, —SH, —N₃, —S(═O)—, imine, ether, ester,aldehyde, ketone, amide, sulfone, acetic acid, cyanide, phosphine,phosphite, aniline, pyridine, or pyrrole.
 5. The multilayer structure ofclaim 1, wherein the hydrolysis promoting agent comprises ethanol,1-butanol, 1-propanol, 2-propanol, 2-butanol, isobutyl alcohol,1-pentanol, 2-pentanol or 2-methyl-2-pentanol.
 6. The multilayerstructure of claim 1, wherein the hydrolysis promoting agent comprisespropylene glycol, ethylene glycol or 1,3-propanediol.
 7. The multilayerstructure of claim 1, wherein the hydrolysis promoting agent comprisesglycerin, trimethylolpropane or pentaerythritol.
 8. The multilayerstructure of claim 1, wherein the BARC layer further comprises asurfactant, a quencher, a thermal acid or thermal base generator orcombinations thereof.
 9. The multilayer structure of claim 1, furthercomprising a planarization layer between the substrate and the BARClayer.
 10. The multilayer structure of claim 9, wherein theplanarization layer comprises spin-on carbon, diamond-like carbon,polyarylene ether or polyimide.
 11. A method of forming a semiconductordevice, comprising: forming a bottom anti-reflective coating (BARC)layer over a substrate, the BARC layer comprising a polymer and ahydrolysis promoting agent capable of absorbing water from ambientatmosphere; depositing a photoresist layer over the BARC layer, thephotoresist layer comprising an organometallic dimer obtained by partialhydrolysis of a precursor organometallic compound represented by theformula R_(n)-M-L_(4-n), wherein M is a metal selected from the groupconsisting of tin (Sn), antimony (Sb) and indium (In), R is an organicligand with 1 to 30 carbon atoms bound to M with a metal-carbon bond, Lis a hydrolysable ligand, and n is an integer of 1 or 2; thermallycuring the photoresist layer, thereby causing hydrolysis of theorganometallic dimer in the presence of water and subsequentcondensation of the hydrolyzed organometallic dimer to form anorganometallic oxide hydroxide cluster, wherein the hydrolysis promotingagent absorbs water from ambient atmosphere to cause the completehydrolysis of the organometallic dimer; patterning the photoresist layerto form a patterned photoresist layer; and etching the BARC layer usingthe patterned photoresist layer as an etch mask.
 12. The method of claim11, wherein the hydrolysis promoting agent comprises a high boilingpoint solvent having a boiling point greater than 180° C.
 13. The methodof claim 12, wherein the high boiling point solvent comprises dimethylsulfoxide (DMSO), dimethylacetamide (DMAC), dimethyl formamide (DMF),toluidine, p-toluene sulfonic acid, pyridine, chlorobenzene,tetrachloroethane, cumene, propionic acid, 1-hexanol, m-butanol oracetic acid.
 14. The method of claim 11, wherein the hydrolysispromoting agent comprises a diffusible molecule represented by thefollowing formula:R₁—X, wherein: R₁ is an alkyl, cycloalkyl or aryl group; and X is —I,—Br, —Cl, —NH₂, —COOH, —OH, —SH, —N₃, —S(═O)—, imine, ether, ester,aldehyde, ketone, amide, sulfone, acetic acid, cyanide, phosphine,phosphite, aniline, pyridine, or pyrrole.
 15. A method of forming asemiconductor device, comprising: forming a first material layer over asubstrate; forming a second material layer over first material layer,the second material layer comprising a polymer, a thermal acid generatorand a hydrolysis promoting agent capable of reacting with the thermalacid generator to generate water; applying a precursor solution over thesecond material layer to form a photoresist layer, the precursorsolution comprising an organometallic dimer obtained by partialhydrolysis of a precursor organometallic compound represented by theformula R_(n)-M-L_(4-n), wherein M is a metal selected from the groupconsisting of tin (Sn), antimony (Sb) and indium (In), R is an organicligand with 1 to 30 carbon atoms bound to M with a metal-carbon bond, Lis a hydrolysable ligand, and n is an integer of 1 or 2; baking thephotoresist layer at an elevated temperature, wherein baking thephotoresist layer results in hydrolysis of the organometallic dimer inthe presence of water and subsequent condensation of the hydrolyzedorganometallic dimer forming an organometallic oxide hydroxide cluster,wherein the water is generated by the reaction of the hydrolysispromoting agent and the thermal acid generator; and exposing thephotoresist layer to a patterning radiation to form a patternedphotoresist layer.
 16. The method of claim 15, wherein the hydrolysispromoting agent comprises a mono-alcohol, a diol or a polyol.
 17. Themethod of claim 15, wherein the hydrolysis promoting agent furthercomprises a polar functional group selected from the group consisting of—I, —Br, —Cl, —NH₂, —COOH, —OH, —SH, —N₃, —S(═O)—, imine, ether, ester,aldehyde, ketone, amide, sulfone, acetic acid, cyanide, phosphine,phosphite, aniline, pyridine and pyrrole.
 18. The method of claim 15,wherein exposing the photoresist layer to the patterning radiationcomprises illuminating the photoresist layer using a radiation beamhaving a wavelength less than 250 nm.
 19. The method of claim 18,wherein exposing the photoresist layer to the patterning radiationcomprises illuminating the photoresist layer using a KrF excimer laser,ArF excimer laser, an EUV or an e-beam radiation.
 20. The method ofclaim 15, wherein the photoresist layer further comprises a surfactantor a quencher.